adding “cmap E e” in vimrc breaks plugins

Question

I'm using lots of vim plugins like nerdtree, fugitive etc.

recently I was adding some new mappings and some of the plugins broke

I traced it down to the following line

cmap E e

WTF? :) why would it break NerdTree?

UPDATE: forgot to mantion how it breaks ;). I get the following error:

E492: Not an editor command: :NeRDTreeToggle

UPDATE2: Duh! I now know what happens. mapping E to e turns NERDTreeToggle into NeRDTreeToggle so the new question is how to map E to e properly? i.e. so that ":E foo.txt" will do the same as ":e foo.txt"

Answer 1

I found the solution myself:

command -nargs=* -complete=file E e <args>

Answer 2

For I added below:

call pathogen#infect()
call pathogen#helptags()
filetype plugin indent on·
syntax on

in .vimrc file